US1931436A - Electrical precipitating apparatus - Google Patents

Description

Oct. 17, 1933. w. g-i

ELECTRICAL PRECIPITATING APPARATUS Filed Oct. 30, 1931 3 Sheets-Sheet l INVENTOR.

Oct. 17, 1933.

w. DEUTSCH ELECTRICAL PRECIPITATING APPARATUS Filed Oct. :50. 1931 5 Sheets- Sheet 2 IINVENTOR.

MEz/lerDevisc/a. B Y m, 2 MM A TTORNE YS.

Oct. 17, 1933. w. DEUTSCH ELECTRICAL PRECIPITATING APPARATUS Filed Oct.

30, 1951 3 Sheets-Sheet 3 I N V EN TOR Wa /fie!" devise/z ATTORNEYS.

Patented Oct. 17, 1933 1,931,436 ELECTRICAL PRECIPITATING APPARATUS Walther y,

Deutsch, Frankfort-on-the-Main, Gerassignor to International Precipitation Company, Los Angeles, Calif., a corpora-.

tion of California Application October 30, 1931, Serial No. 572,199,

and in Germany November 3, 1930 7 Claims.

This invention relates to improvements in apparatus for separation of suspended particles from gases by electrical action, and the main object of the invention is to increase the operative effectiveness of such apparatus, so as to provide for maximum working capacity and emciency, for apparatus of a given size and cost.

This object I attain, according to the present invention, by providing means whereby the mechanical actions due to movement of the gas stream itself, operate concurrently with and reenforce the electrical action due to the electrical field produced in the apparatus, so as to produce increased separating effect.

In electrical precipitating apparatus as usually constructed, the gas to be treated passes between discharge and collecting electrodes, in a direction parallel to the surfaces of such electrodes, an electrical potential difference being maintained between the electrodes so as to produce an electrical field acting to cause suspended particles in the gas to move toward and be deposited, mainly, -on the collecting electrodes.

With such a construction the motion of the gas does not, in general, contribute directly to the separating operation, but rather tends to interfere therewith, by reason of the tendency of the moving gas to dislodge, entrain and carry forward the separated material.

My invention provides for supplying and distributing the gas in the precipitating fine or chamber in such manner that the motion of the gas is largely toward the surface of the collecting electrode and is therefore concurrent with and auxiliary to, the motion of the suspended particles toward the collecting electrode under the action of the electrical field, thereby obtaining maximum separating and collecting effect.

The accompanying drawings illustrate embodiments of my invention and referring there- Fig. 1 is a vertical section of a form of the. invention, comprising a single set of discharge and collecting electrodes.

Fig. 2 is a section on line 2-2 in Fig. 1, with a part of the collecting electrode broken away.

Figs- 3 and 4 are vertical sections of modified 5 forms. of the invention.

Fig. 5 is a vertical section of a form of the invention comprising a plurality of sets of electrodes.

h Fig. 6 is a horizontal section of a modification of the collecting electrode construction.

Fig. '7 is a vertical section of a modflcation of the form of invention shown in Fig. 4.

Fig. 8 is a horizontal section of a precipitator comprising a plurality of electrode units of the form shown in Fig. '7.

Fig. 9 is a section on line 9-9 in Fig. 8.-

Fig. 10 is a perspective and Fig. 11 a vertical section of a further modification of the collecting electrode.

Fig. 12 is 2. tion.

Figs. 13 to 16 are horizontal sections of other forms of the invention.

In the form of the invention shown in Figs. 1 and 2, the gas to be treated enters the precipi- 7o tating chamber through the discharge electrode, the latter being shown as a tubular conducting member, mounted by an insulator 2 on a supporting base 3, and communicating at its lower end with an inlet pipe 4, for the gasf Said tubular member 1 is provided with perforations 5 through which the gas passes into the precipitating chamber or space around the discharge electrode, and the edges of these perforations preferably project outwardly to facilitate electrical discharge therefrom.

Surrounding discharge electrode member 1 is a perforate collecting electrode consisting, for example, of rods 6, spaced apart to provide outlet passages 6' for the gas, said rods being 86 mounted on a ring 7 which is connected to supporting base 3 by'ribs 7'. Rods 6 are shown as curved at the top to meet in a top member 6", forming a dome-shaped structure extending over as well as around the discharge electrode, and 90 the latter is shown as provided with outlet openings 5 at its top for directing gas toward the top portion of the collecting electrode. It will be seen, therefore, that the outlet passages 6 constitute the sole means for outflow of gas from the space between the discharge and collecting electrodes.

Base 3 is shown as formed with a hopper 8 extending below the collecting electrode members to receive collected material therefrom, and 1 with discharge openings 9 in its bottom controlled by gates 9'.

The tubular discharge electrode 1 is shown as provided'with a hood 10 for protecting the insulator 2 from material falling from the elec- 0 trodes, and the lower end 11 of the discharge electrode is preferably serrated to cooperate with the grounded inlet tube 4, in precipitating suspended material from the gas between said parts, so as to prevent deposition of such material on perspective of a further modifica- 65 the insulator. A connection 12 leads through an electrical discharge from electrode 1 and movement of the suspended particles toward the collecting electrode by the action of the electrical field.

The openings 5 in the discharge electrode may be varied in spacing or in area so as to provide for equalization of flow into the precipitating chamber at all parts thereof. The gases to be treated, and carrying suspended material such as dust, fume or mist, pass through pipe 4 at a. more or lesshigh velocity into electrode tube 1, and pass out radially through discharging openings 5 and arrive at a greatly decreased velocity at rods 6 of the cage-like collecting electrode.

At the same time, an electrical field is main- ,tained between electrodes 1 and 6, and causes migration or movement of the particles also toward the collecting electrode. The suspended particles are thus carried to and precipitated on the collecting electrode by the combined effect of the gas stream and of the electrical field. When the particles have been deposited on rods 6, the clean gases pass out through the interstices or passages 6 between said rods, either into the atmosphere or into suitable recovering or conducting means. Both the discharge electrodes and ,the collecting electrodes may be cleaned by rapping or shaking in known manner.

In the form of the invention shown in Fig. 3, the perforated and grounded collecting electrode 14 is closed at the top by cover 15, on which is mounted insulator 16 carrying the wire or rod discharge electrode 17. Collecting electrode 14 may consist of a perforated shell or tube of mesh material and is mounted on a collecting chamber 18 through the wall of which the electric current is led by means of insulated connection 20 to discharge electrode 17. Chamber 18 is provided with inlet 21 for the gases, and with a hopper 19 having discharge gate 23. Collecting electrode 14 is so formed thatit allows uniform flow of gas throughout its longitudinal area. For this purpose the screen meshes or perforations of said electrode may, as shown, be more numerous as the gas passes closer toward insulator 16 and cover 15, so that the resistance to gas flow decreases toward the top.

Another arrangement is possible according to this invention, as shown schematically in Fig. 4. Insulator 24 projects into a hemispherical chamber formed by a screen or grid-type collecting electrode 25. A rod 2'7 connected to a high tension line is passed through insulator 2'7, which rod carries a discharging point 28 placed about in the center of the semicircular chamber. The

grounded electrode 25 is connected to a gas inlet tube 29 provided with deflecting means 30 and 31 to deflect the gas flow in such manner that a predominantly radial current in the direction of the arrows is produced, and passes through perforations or meshes of electrode 25.

An electrical field is maintained between discharge point 28 and the grounded collecting electrode 25, sufllcient to produce precipitation in the surface of electrode 25, the velocity of the dusty gases passing into-tube 29 toward the greater surface of electrode 25, being decreased in such manner that there is a relatively strong electrical deflection, and no charged particles can escape from the openings ofelectrode 25.

An arrangement suitable for a larger gas volume is shown in Fig. 5. Here 32 represents a common inlet chamber for the gases passing in at inlet 33. This chamber is closed at the bottom by means of common hopper 34 and at the top by plate 35 which supports the tubular perforated collecting electrodes 36. Said tubular electrodes open at their lower ends into the inlet chamber 32 and are closed at the top. The discharge electrodes consist of wires or rods 38 and are mounted on a common supporting bar 39, and extend upwardly within the respective tubular collecting electrodes 36. Said bar 39 is connected to a suitable high tension line and is carried on insulators 40 and 41. chamber 42 with outlet 43, is provided above precipitation chamber 32 and around the collecting electrodes 36. The outlet 43 communicates directly with said outlet chamber outside the collecting electrodes, and since the upper ends of the collecting electrodes are closed, the outflow of gas from said collecting electrodes is, as before, caused to take place wholly through the perforations of said electrodes. The gas to be treated enters at 33, deposits the dust in passing through electrodes 36 on the electrode walls, passes into chamber 42, and as cleaned gas, passes out at 43.

The collecting electrodes may be rapped or tensioned from time to time by means of bar 44 projecting from chamber 42, and adapted to receive the impact of movable hammer means 44' to allow the dust to fall into hopper 34.

In case the collecting surfaces are not sufficient, they may be increased in size by placing a second or third etc. grounded concentric electrode over the perforated collecting electrode, which will attract and hold any charged particles which may pass out of the inner elec-.

trode as shown in Fig. 6. Here 45 indicates a hemispherical electrode according to Fig. 4, surrounded by a second perforated electrode 46 and a third perforated electrode 47. This arrangement may, of course, also be used for pipe cylinders according to Fig. 3, or cage-type as in Fig. 1.

Fig. 7 shows another form of the invention. A perforated cylinder 45 provided with a perforated bottom 55 is used here instead of a heimspherical electrode as 25 in Fig. 4. The wire or rod discharge electrode 56 projects into the jar-type chamber or collecting electrode. As the arrows show, the gas current is directed A clean, gas

substantially radially, at least in the vicinity of the perforated electrodes 54 and 55.

Cleaning greater volumes of gases by means of the jar-type screen according to Fig. 7 may be done as shown in Figs. B and 9, where the gas enters a chamber 58 at 57 and passes out at outlet 59. The jar-type precipitator units 60 are here set in transverse walls 61 of the chamber 58.

The discharge electrodes 62 are mounted on transverse arms 63 carried by bars 64 which are mounted on insulators 65 and 66" supported on housing of chamber 58. Suitable high tension connections are made to bars 64, and the housing of chamber 58 is grounded. The dust falls during rapping through the meshes of the electrodes 60 into hopper 67.

A further example of the invention is shown in Figs. 10 and 11, in which the collecting electrode consists of a number of circular rings 68 placed one above the other, and which are separated by spacing and supporting means, not

Shown, at such distances or spacings that there ,or of a perforated shell, as shown at 99' '70- is only a small space between adjacent rings. The dusty gases passing through the inside of the chamber formed by these rings, pass outward as shown by arrows, and in passing through the spaces between the rings,v allow the particles suificient time to be deposited on the walls of the rings, by means of electrical attraction as well as by force of gravitation.

Fig. 12 shows another construction illustrating that precipitator tubes may be left open at the end opposite the inlet, without departing from this invention. In said figure the precipitator is shown as comprising a casing '70 with two transverse diaphragms or partitions '71 and '72 between which extend tubular perforated collecting electrode members '77 which open at their lower ends into an inlet chamber '73 communieating with an inlet pipe '14 for the gas to be treated, and at their upper ends into a dead space between the top partition '71 and the top for the casing '70. An outlet '75 for the cleaned gas communicates with the chamber '76 between the upper and lower partitions "71 and '72, the gas passing from the precipitating chambers within electrodes '77, through the perforations in said electrodes into chamber '76 and then through outlet '75.

The discharge electrodes are shown as wires '78 hung from cross bars '79 mounted on a rod which is supported by an insulator 81 on the top member '70 aforesaid and connected to a high tension electric line. wires '78 may betensioned by weights 82 and spaced in proper position by frame 83. A hopper 69 is provided below chamber '73.

, As shown-in Fig. 13, the construction may be such that the gas enters the tubular perforated collecting electrodes at both ends thereof, said electrodes, indicated at 84, opening at both ends into an inlet chamber 88 and extending across a gas outlet chamber 86, the gas inlet 89 and gas outlet 90 being connected respectively to the chambers 88 and 86 so that the gas passes tubular perforatedfrom chamber 88 into the collecting electrodes 84 at both ends thereof, and then outwardly through the perforate walls of said electrodes to the chamber 86'. The discharge electrodes 91 are shown as mounted on bars 92 supported on insulators 93 and 94 and connected by conductor 95 to any suitable high tension supply line.

In the construction types shown, the discharge electrode and the collecting electrode form an electrical field which extends also out through the meshes or perforations of the collecting electrode. A third electrode may .be added, of such a potential that the resulting electric field of all three electrodes weakens the penetrating action of the field which would be produced without the third electrode, and therefore would influence the particles still passing out through the meshes of the collecting electrode and cause them to return to this electrode.

. Fig. 1'4 shows an example in which 9'7 is a discharge electrode and 98 is a collecting elec trode forming a cage. An auxiliary electrode comprised of rods, as shown at 99in Fig. 14, in Fig. 15, is placed on the outside of electrode 98, said auxiliary electrode having the same polarity as.

the discharge electrode and having either the same potential as this or having a graded potential, so that for example the outer electrode 99 or 99' is connected to a 10,000 volt connecacids, etc.)

Discharge electrode tion, while discharge electrode 9'1 is on a 40,000

volt connection.

Centrifugal or impact force may be used also for precipitation of the particles, as shown in Fig. 16, where the precipitator outlets in collecting electrode 101 are formed as bent nozzles 100. A cylindrical shell 102 is shown as surrounding the collecting electrode to collect any particles passing from nozzles 101, in case the precipitation of the particles on the collecting electrode is not complete.

The perforated collecting electrodes above described constitute in effect, filter or screens through which the gases pass out of the precipitating chamber. Such screens may be either of perforated sheet metal or of wire mesh. The materials of construction for these filters or screens utilized as collecting electrodes, are of course dependent on the nature of the substance to be precipitated, (dusts, sludge, liquids, such as or semi-conducting materials may be used. It is also possible in suitable cases to use nonconductors which become, during precipitation, superficially coated with a conducting layer or soaked with conducting substances.

Fibrous materials may be used which are made conductive in known manner, as by bronzing or metallizing. The electrodes may also be of the deformable type, such as bags or flexible tubing, which may be tensioned for cleaning.

1 The form of the collecting electrode is mostly dependent on its material and the type most suitable for the installation. Conical bags may be used advantageously, in order to obtain a graded electrical field.

Very thickly meshed materials may be used for the precipitation of poisons, bacteria, etc., by combined use of precipitation and adsorption. This is especially suitable for respirators or gas masks, as this type presents less resistance to the passage of the cleaned air than those depending only on adsorption.

It will be apparent from the foregoing description and-from the drawings that the openings for the flow of gas through the collecting electrodes or through the discharge electrodes may vary greatly in size, shape, number and arrangement, and the term perforations is intended broadly to include any such openings for the flow of gases through the electrodes.

The method described may also be easily combined with any known methods of electrical precipitation. Also, by electrically charging the filter surfaces from outside, the dust particles which might escape are again brought into the field of a corona discharge and can be precipitated on the outside of the filter surfaces.

The above described invention provides a precipitator which with'intensive'action, requires a 3 7 small space and less material, and therefore costs less to build. Its principle is in short, that of an electrical bag filter", through whose meshes all the gas must pass, while substantially all of the dust particles are retained, but whose. meshes can be made large enough so that in comparison with a bag filter only low draftlosses result.

It is possible with the describedconstruction to conduct practically all of the suspended particles to the collecting electrodes and thus raise 3 the efllciency. A further advantage lies in the fact that previously charged suspended particles entering into the electric field are attracted when they pass through the perforation of the collectingv electrode and are securely deposited.

1 iii By using a radial gas flow, the direction of the gas flow is more or less the same as the lines or direction of the electrical field lines of the precipitation field, and thus every particle is conducted most rapidly to the collecting surface, that is, to the place where it is to be precipitated, and the following is to be noted.

The electrical field which acts on the particles as they pass through the perforated collecting electrode, is especially effective when the gas velocity at or near the collecting electrodes is as great as is the migration velocity of the particles in relation to the velocity of the gas flow.

The requirement of radial outflow velocity is met in this way that the velocities in the case of spherical symmetrical form act inversely as the second power and in the case of a cylinder act as the first power of the radius, so that very low velocities occur near the collecting electrode, while the gas may enter at the inlet side at normal velocity.

A gas outlet through a free opening, as pre viously used in construction, requires a larger space and therefore entailsa higher construction cost.

In practice it has been shown advantageous to maintain the gas velocity at the collecting electrode about the same as the electrical migra-,

tion velocity (of the particle). One can operate satisfactorily at an electrical travel velocity of 5 cm. per second; so that the gas velocity should also be kept as low as 5cm. per second.

In comparison to the usual gas velocity in precipitators, this velocity is very low. Despite this fact, a smaller electrode surface is required for cleaning a certain gas volume per hour by means of this herein described method, than ordinarily required. This may be shown in the following example:

A gas volume of 0.13 cubic meters per second passes at a velocity of 5 cm. per second through a cylinder 3 meters in length, as described above, which is of the usual diameter of electrical precipitation technique of 274 mm. If the gas is cleaned in another manner, namely, by passing it through a similar cylinder or tube which has a free outlet opening and no perforated wall and the usual velocity of 1 meter per second is used, which, with the given' tube length of 3 meters would. give a fairly good efliciency, the result would be a gas volume of only 0.06 cubic meters per second, and therefore only one-half the gas volume could be cleaned'as compared with the method on which this invention is based.

I claim:

1. An apparatus for electrical precipitation'of suspended particles from gases comprising discharge electrode means, perforate collecting electrode means extending around the discharge electrode means, said discharge and collecting electrode means being provided with electrical connections for maintaining high potential difference therebetween, andmeans for supplying and distributing gas to be treated into the space between the discharge and collecting electrode means in such-manner that the gas flows substantially wholly away from the discharge electrode means toward and through the perforate collecting electrode means, so that the movement of suspended particles in the gas due tov the movement of the gas stream is concurrent with and reenforces the movement of such particles due to the electrical field between the electrodes, the perforation in the collecting electrode means constituting "substantially the sole means for outflow of gas from said space.

2. An apparatus for electrical precipitation of suspended particles from gases comprising a discharge electrode, a tubular perforate collecting electrode surrounding the discharge electrode, said electrodes being provided with connections for maintaining high potential difference therebetween, and means for supplying gas carrying suspended particles into the space between the electrodes and drawing such gas away from the discharge electrode and through the perforate collecting electrode.

3. An apparatus as set forth in claim 2 and.

comprisingin addition, means defining a cham-' ber surrounding the collecting electrode and outlet means for conducting gas from said chamber.

4. An apparatus for electrical precipitation of suspended particles from gases comprising a gas inlet chamber, a plurality of tubular collecting electrodes communicating with said chamber, said collecting electrodes having perforate walls, discharge electrode means extending within the respective tubular collecting electrodes and insulated therefrom, said discharge and collecting electrodes being provided with connections for maintaining high potential difference therebetween, and a gas outlet chamber inclosing said collecting electrodes and provided with outlet means communicating directly with said chamber outside said collecting electrodes.

5. In an apparatus for electrical precipitation of suspended particles from gases, a hollow discharge electrode member provided with perforations in the wall thereof, a collecting electrode surrounding and spaced from said discharge electrode and provided with perforations constituting substantially the sole means for outflow of gas from the space between said discharge and collecting electrodes, and inlet means communicating with the interior of said discharge electrode.

6. In an apparatus for electrical precipitation electrode, said collecting electrode being also provided with perforations constituting substantially the sole means for outflow of gas from the space between said discharge and collecting electrodes.

7. In an apparatus for electrical precipitation of suspended particles from gases, a hollow dis charge electrodemember provided with openings in the wall thereof and with outwardly projecting discharging portions formed to promote electric discharge therefrom, inlet means communicating with the interior of said discharge electrode, and collecting electrode means concentrically surrounding and spaced from said discharge electrode member and provided with openings constituting substantially the sole means for outflow of gas from the space between said discharge electrode member and said collecting electrode means.

* WAL'I'HER DEUTSCH.

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